An Aegisub macro which automatically compresses timestamps for 23.976fps sources that have been converted to 24fps

23.976fps-to-24fps-subtitles.lua

script_name = "23.976fps to 24fps Subtitles"
script_description = "Automatically compress timestamps for 23.976fps sources that have been converted to 24fps"
script_author = "natyusha"
script_version = "1.0"

function f23_976fps_to_24fps(subs)
    -- Scale factor for 23.976fps to 24fps conversion (23.976 / 24)
    local scale_factor = 23.976 / 24  -- Approximately 0.999 (999 / 1000)

    -- Process all subtitle lines
    for i = 1, #subs do
        local line = subs[i]
        if line.class == "dialogue" then
            -- Apply time compression (in milliseconds)
            line.start_time = line.start_time * scale_factor
            line.end_time = line.end_time * scale_factor
            subs[i] = line
        end
    end

    aegisub.set_undo_point(script_name)
end

function check_subtitle_exists(subs)
    return #subs > 0
end

aegisub.register_macro(script_name, script_description, f23_976fps_to_24fps, check_subtitle_exists)